This invention relates to an internal combustion engine and more particularly to an improved valve timing and induction system for an internal combustion engine.
As is well known, internal combustion engines are utilized for a wide variety of purposes. Many of these applications, such as when operating motor vehicles, demand the engine operate over widely varying load and speed ranges. This varying loading and speed of operation for the engine gives rise to substantial difficulties in engine design. That is, an engine that is designed to run at a particular speed and load may be inefficient or not run as well as desired at other speeds and loads. Therefore, a wide variety of techniques have been employed in order to try to improve engine running throughout its speed and load range.
One type of system employed to improve engine performance under varying conditions is the use of variable valve timing. That is, the timing of opening and closing of either or both of the exhaust and intake valves may be varied during engine running. By doing this, the optimum valve timing for each condition can be chosen.
In connection with the air induction system for an engine it has also been found that in the introduction of turbulence into the combustion chamber can be very effective in improving flame propagation and combustion under low speed/low load running conditions. However, the type of turbulence generating devices frequently employed restrict airflow and can thus sacrifice high speed performance. Therefore, it has been proposed to use devices such as tumble valves in the induction system that can be controlled to induce turbulence under some running conditions and to permit unrestricted air flow under other running conditions.
It has been found advantageous to combine the use of variable valve timing and flow control in the same engine. However, and in accordance with an important feature of this invention, it has been discovered that these systems have an interrelated operation that can be utilized to obtain optimum running if the control of the valve timing and of the flow control valve are coordinated with each other in a proper sequence.
Systems have also been proposed in which there is not a direct mechanical connection between the accelerator pedal or other operator controlled speed and load control and the throttle valve or other controlling system of the engine. These systems are frequently referred to as "fly by wire" systems.
In connection with the use of flow controlling valves, it has been also found that the position of the flow control valve can change the speed at which the engine is operating all other things being equal. Therefore, it is possible to utilize in a fly by wire system a control where the engine speed can be varied by holding the throttle valve in a fixed position and varying the position of the flow control valve. This also can permit the throttle valve to be opened wider than would be normal under the conditions and thus improve acceleration.
It is, therefore, a still further object of this invention to provide an engine having a speed control wherein the speed or output of the engine are varied by controlling both the throttle valve and the flow control valve.
Finally, where engines have the capability of adjusting both the timing of the intake and exhaust valves, these can be operated either together with each other or in some sequence.
It is a further object of the invention, therefore, to provide the optimum range of adjustment for the intake valve and for the exhaust valve independently of each other when both are independently controlled.